The present invention relates to a flame-retardant polyamide composition excellent in mechanical properties, e.g., flowability and toughness, and in resistance to reflow heat, and also to electric and electronic device members, e.g., connectors, made of the flame-retardant polyamide composition, more particularly to a flame-retardant polyamide composition suitable for forming electric and electronic device members, e.g., fine-pitch connectors which are thin and short in distance between the connector terminals, and to heat-resistant electric and electronic device members, e.g. connectors, made of the flame-retardant polyamide composition.
The dip method is a normal choice for soldering connectors onto a print-circuit board. Recently, reflow (surface mounting) soldering has been developed as the method for high-density mounting. It coats a print-circuit board with a creamy solder by the printing techniques, puts the device members (e.g., connector) thereon, and heats and melts the solder by infrared ray and/or hot air, to mount these members by the molten solder (surface mounting). The connector material must be highly resistant to heat, when surface-mounted by the reflow soldering, because it is exposed to a high temperature of 230 to 240xc2x0 C. by infrared ray or hot air in the reflow furnace.
Polyamide has been used as the material for molding electronic device members, because of its moldability into a desired shape after being molten under heating. In general, the polyamides widely used for the above purposes include nylon 6 and nylon 66. These aliphatic polyamides, however, are not sufficiently resistant to heat as the materials for the surface-mounted members, which are exposed to high temperature, although having good moldability. The surface mounting, therefore, needs highly heat-resistant polyamides, which has led to development of nylon 46. It is more resistant to heat than nylon 6 and nylon 66, but has a disadvantage of high water absorptivity, which may cause problems. The electric or electronic device member of nylon 46 resin composition, when it absorbs water, may undergo dimensional changes caused by the moisture, and blister under heating during the reflow step. In order to solve these problems, an aromatic polyamide has been developed, as disclosed by Japanese Patent Laid-Open Publication No.53536/1984. It is derived from an aromatic dicarboxylic acid, e.g., terephthalic acid, and an aliphatic alkylene diamine, and is higher in resistance to heat, mechanical strength and rigidity and lower in water absorptivity than nylon 66 and nylon 46.
A polyamide resin is inherently self-extinguishing in nature, but must be incorporated with a flame retardant for surface-mounted members required to clear the high flame retardancy standard, e.g., V-0 specified by UL94. One of the common methods to improve flame retardancy of polyamide is incorporation of a flame retardant, e.g., a halogen compound. For example, a composition of polyamide is incorporated with a halogenated polystyrene (Japanese Patent Laid-Open Publication No. 47034/1976), with a brominated polystyrene represented by Ferro""s Pyrocheck 68PB, (Japanese Patent Laid-Open Publication No. 66755/1991), with a polybrominated styrene, which is produced by Polymerization of brominated styrene and is more thermally stable than brominated polystyrene (Japanese Patent Laid-Open Publication No. 320503/1993, WO 98/14510), and with a condensate of brominated phenol (Japanese Patent Laid-Open Publication No2100/1981). These halogen-based flame retardants do provide flame retardancy and improve flowability characteristics, but tend to deteriorate mechanical properties, e.g., toughness.
Recently, surface-mounted members, e.g., connectors, are becoming thinner and shorter in pitch. As such, the resin for these members are required not only to be higher in resistance to heat and flowability but also in toughness, in order to prevent cracking of the formed member, e.g., connector, when a metallic terminal is pushed thereinto.
Therefore, a flame-retardant polyamide composition excellent in flame retardancy, flowability and toughness has been increasingly in demand for these surface-mounted embers, e.g., connectors.
Some of the methods to improve mechanical properties of polyamide, e.g., toughness, include incorporation of a maleic polyolefin or SEBS. However, mere addition of the above compound will deteriorate flowability of polyamide.
It is considered that dispersion of the flame retardant particles uniformly and finely will control property deterioration caused by the retardant. However, no method has been investigated to reduce retardant particle size in a base resin dispersed with the retardant and glass fibers, or to measure the retardant particle size. No attempt has been made to establish the relationship between flame retardant particle size and toughness of a resin composition.
Japanese Patent Laid-Open Publication No.320503/1993 discloses number- and weight-average molecular weights of polybrominated styrene, discussing that mechanical properties deteriorate as they decrease and flowability decreases as they increase, and that a flame retardant preferably has an average diameter of 20 xcexcm or less, more preferably 10 xe2x96xa1m or less, when it is dispersed in a polyamide resin composition. However, it is silent whether or not size of the flame retardant dispersed in the polyamide resin composition is concretely measured. The inventors of the present invention have, measured the particle size to find that it is very large. The specification is also silent about the concrete method for finely dispersing the particles and concrete discussion on the relationship between the particle size and composition properties.
The invention has been developed to solve the problems involved in the conventional techniques. It is an object of the invention to provide a polyamide composition excellent in flame retardancy, good in flowability and high in toughness.
It is another object of the invention to provide electric and electronic device members made of the flame-retardant polyamide composition.
The flame-retardant polyamide composition of the present invention comprises:
(A) 20 to 80% by weight of an aromatic polyamide, composed of recurring units of dicarboxylic acid component unit and diamine component unit, the former composed of 30 to 100% by mol of a terephthalic acid component unit and 0 to 70% by mol of an aromatic dicarboxylic acid component unit other than terephthalic acid and/or 0 to 70% by mol of a C4-C20 aliphatic dicarboxylic acid component unit and the latter composed of an aliphatic diamine component unit and/or an alicyclic diamine component unit; and having an MFR of 40 to 300 g/10 minutes, determined at a load of 2,160 g and temperature of 10xc2x0 C. plus melting point, and melting point exceeding 290xc2x0 C.;
(B) 5 to 50% by weight of an inorganic reinforcing agent,
(C) 5 to 40% by weight of a bromine-based flame retardant, containing at least one type of polybrominated styrene obtained by polymerization of brominated styrene, and
(D) 0.1 to 10% by weight of an antimony-containing compound and/or zinc-containing compound oxide, the components (A) to (D) totaling 100% by weight,
wherein, the polyamide composition has flame retardancy equivalent to V-0 determined in accordance with the UL-94 specification, and the bromine-based flame retardant has a number-average particle size of less than 0.90 xcexcm in the polyamide composition, when it is pelletized.
The flame-retardant pelletized polyamide resin composition of the present invention comprises:
(A) 20 to 80% by weight of an aromatic polyamide, composed of recurring units of dicarboxylic acid component unit and diamine component unit, the former composed of 30 to 100% by mol of a terephthalic acid component unit and 0 to 70% by mol of a C4-C20 an aromatic dicarboxylic acid component unit other than terephthalic acid and/or aliphatic dicarboxylic acid component unit and the latter composed of an aliphatic diamine component unit and/or an alicyclic diamine component unit; and having an MFR of 40 to 300 g/10 minutes, determined at a load of 2,160 g and at a temperature of 10xc2x0 C. plus melting point, and melting point exceeding 290xc2x0 C.;
(B) 5 to 50% by weight of an inorganic reinforcing agent,
(C) 5 to 40% by weight of a bromine-based flame retardant, containing a least one type of polybrominated styrene obtained by polymerization of brominated styrene, and
(D) 0.1 to 10% by weight of an antimony-containing compound and/or zinc containing compound oxide, the components (A) to (D) totaling 10% by weight,
wherein, the polyamide extracted with concentrated sulfuric acid from the pelletized polyamide resin composition has a viscosity of 60 to 110 ml/g.
The formed article of flame-retardant polyamide composition of the present invention comprises:
(A) 20 to 80% by weight of an aromatic polyamide, composed of recurring units of dicarboxylic acid component unit and diamine component unit, the former composed of 30 to 100% by mol of a terephthalic acid component unit and 0 to 70% by mol of an aromatic dicarboxylic acid component unit other than terephthalic acid and/or 0 to 70% by mol of a C4-C20 aliphatic dicarboxylic acid component unit and the latter composed of an aliphatic diamine component unit and/or an alicyclic diamine component unit;
(B) 5 to 50% by weight of an inorganic reinforcing agent,
(C) 5 to 40% by weight of a bromine-based flame retardant, containing at least one type of polybrominated styrene obtained by polymerization of brominated styrene, and
(D) 0.1 to 10% by weight of an antimony-containing compound and/or zinc containing compound oxide, the components (A) to (D) totaling 10% by weight,
wherein, the bromine-based flame retardant has a number-average particle size of less than 0.90 xcexcm.
The polyamide extracted with concentrated sulfuric acid from the above formed article preferably has a viscosity of 60 to 110 ml/g, and the formed article normally has flame retardancy equivalent to V-0 determined in accordance with the UL-94 specification.
The electric or electronic device member of the present invention is made of the flame-retardant polyamide composition or pelletized polyamide resin composition of the present invention, formed into a desired shape
The inventors of the present invention have found that a combination of specific aromatic polyamide and a specific flame retardant can uniformly reduce size of the flame retardant particles, and give the flame-retardant polyamide composition of high flowability and toughness. The flame-retardant polyamide composition can give finely pitched electric or electronic device members recently in demand, and reduce risk of thermally damaging these members even when they are exposed to high temperature, e.g., during the reflow soldering step.